The invention concerns an electrical resistor, especially a temperature-dependent measuring resistance with rapid response time, having a conductor path (printed circuit) provided with at least two connection contact fields, which are arranged on an electrically insulating surface of a substrate, wherein a portion of the conductor path spans at least one recess of the substrate in a bridge-like manner, and the conductor path is arranged in a plane. The invention also relates to a process for manufacturing the electrical resistor.
A temperature measuring arrangement (radiation thermometer) is known from German published patent application DE 39 27 735 A1 with a temperature-sensitive thin film resistance, which is applied meander-shaped to a plastic sheet which is stretched over a cavity of a substrate material. A circuit board or a carrier of epoxide resin is provided as a substrate. Such a temperature measuring arrangement is only suited for use in an environment with temperatures below 200.degree. C., owing to the low thermal stability of synthetic resin.
Furthermore, from German published patent application DE-OS 23 02 615, a temperature-dependent electrical resistor of resistance material is known, which forms a winding conductor path as a thin layer, which is applied over a thin foil. The foil made of polymer plastic spans with its uncoated side a recess in a carrier element which, for example, consists of copper, wherein the recess has the same shape as the conductor path and aligns with it in a direction perpendicular to the foil plane. Here, it is a matter of a temperature measuring arrangement which requires a high technical expenditure for the requisite precise overlaying of conductor path and recess.
It is known from German patent DE 30 15 356 C2 that electric circuits in thick layer technology are preferably manufactured on ceramic, plate-shaped substrates by imprinting pastes whose active material consists of metal powders, glass or glass ceramic powders, or mixtures of glass and metal oxides. For manufacturing rapidly responding sensors for temperature measurement, temperature-sensitive thick layer resistors are applied to self-supporting layers, which are obtained by paste screen-printing with the aid of a filler gasifiable under the action of temperature and cover a subsequently formed hollow space. Here, it is a question of a relatively expensive process.
Furthermore, from German published patent application DE 38 29 765 A1 or U.S. Pat. No. 4,906,965, a platinum temperature sensor is known, in which a platinum resistance path with at least two ends is mounted on a surface of at least one ceramic substrate. For manufacturing it, a platinum conductor path in the form of a meander-zigzag pattern is applied to the inner surface of a ceramic sheet and subsequently shaped into a roll, wherein breaks with adjusting bridges are provided between adjacent points of the conductor path pattern for the purpose of adjustment. The ceramic substrate is fired together with the applied platinum resistance. The platinum resistance is resistant toward the ambient atmosphere and moisture owing to sealing measures. In addition, after adjustment, the lead-in openings and conductors necessary for this are sealed off by means of a ceramic coating or glass paste. The comparatively high heat capacity turns out to be problematic with such an arrangement, which does not make possible a rapid response with sudden temperature changes, without further measures, and which reproduces an exact measured value only after execution of a transition function.
A further embodiment of a resistance element as rapid temperature sensor is known from German published patent application DE 38 29 195 A1. Here, the resistance element is constructed as a layer resistor of platinum paste, which is accommodated in a bubble made of glass ceramic, which is arched on an electrically insulating ceramic substrate. Here, the self-supporting arched resistor layer is to be regarded as problematic with respect to mechanical stresses, for example, shock, pressure or vibration during use in harsh environments.